Thank you, you help me a lot to understand the trouble : the appearance of special ans Greek Character depends only on the font used.
Example of different shapes associated to différent fonts 
I have many pages written with a lot of formulas, all the proofs are styled with my handwrite-font which is associated to a wrong shape.
I don't want to change the font, and I can't change the font for each character.
I'm looking for an option with which we can force the shape of special and greek characters
